The lighting difference in Sonic Adventure are so much better than in the ports. From what I've read, it's because this version used the Dreamcast's LANTERN engine. Which uses colour palettes. So Sonic's model has a sort of icy look in Icecap and a blustery look inside the tornado in Windy Valley.
Also, the lighting in the hubs is so vastly different. Sunset feels like sunset and night feels like night. Especially in the Mystic Ruins. The ports completely mangled this.
sonic adventure will always have my favorite sonic model. partially because i just really like how he looks but partially because i see him in a similar way people see mario in mario 64. i like to imagine he's a little guy who wanders around city blocks and jumps on cars. he's like a cat that occasionally spits out cheesy compressed ryan drummond sound clips